This invention relates to a crank chamber structure for a two cycle internal combustion engine, and more particularly to an improved crank chamber structure and arrangement which provides increased fuel/air transfer capability between the induction system and the combustion chamber so as to improve the power output capability of the engine.
In some multi-cylinder two cycle, crankcase compression internal combustion engines, it is the practice to employ crank webs positioned within the crankcase chamber. These crank webs in connection with sealing members which extend around the crank webs and which are in contact with the cylinder block and the crankcase body serve to partition the crankcase chamber into a plurality of individual crank chambers, one for each cylinder. Although this type of arrangement provides airtight crank chambers wherein the precompression ratio can be increased to improve intake efficiency, it has also previously resulted in very narrowly formed passages in the crank chambers for transfer of the fuel/air mixture to the scavenge passages which makes it difficult to increase the intake quantity to increase engine output.
It is, therefore, a principal object of this invention to provide an improved crank chamber structure and arrangement for a two cycle internal combustion engine which includes an expanded fuel/air transfer passage extending from the intake passage of the induction system to the scavenge passage so that the intake quantity can be increased and wherein the primary compression ratio can be increased so as to increase the power output of the engine.